Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already provide readOnlyHint=true, and the description adds valuable context beyond that: the weighting scheme (WARNING=100/WATCH=66/ADVISORY=33), normalization baseline, daily updates, 10-year history, and the output components (score, elevated volcano names, methodology version). No contradictions detected.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two concise sentences: the first describes the return value and methodology, the second lists use cases. No fluff, front-loaded with key information, and every sentence adds value.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given no output schema, the description compensates by explaining the return components (score, elevated volcano names, methodology version) and behavioral details like daily updates and 10-year history. It is slightly missing an interpretation of the score or edge cases, but is sufficient for a read-only snapshot tool with one optional parameter.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The schema provides 100% coverage of the only parameter ('days') with full description including the Gold tier requirement. The description does not add any extra parameter semantics beyond what the schema already offers, so the baseline of 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb and resource: 'Returns a 0-100 US volcanic alert pressure index' with detailed methodology (USGS HANS weights, normalization to a 5-volcano baseline). This clearly differentiates it from any sibling tool by defining its exact measurement and output.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explicitly states when to call: 'when the user asks about volcano alerts, volcanic activity, eruption risk, volcanic unrest, or natural-hazard exposure, or when timing catastrophe loss-model runs or insured-property risk reviews near US volcanoes.' It gives clear context but does not mention exclusions or alternative tools, so it stops short of a 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.